A wide-angle hydro lens is known, comprising five components, of which the first one is a positive (converging) meniscus with its convex surface facing the object side, the second and the third ones are negative menisci, the fourth one is a negative meniscus cemented to a biconvex lens, the fifth component is a positive meniscus cemented to a negative one, and the sixth component is a biconvex lens. The lens demonstrates adequate correction of aberrations and features a considerable angle of view in water 2ω=90° (in the air 2ω=141°).
The disadvantage of this lens is its insufficient relative aperture (1:2.8).
A fast lens “Electron-1” is known comprising eight components, the first of which is a negative meniscus cemented to a biconvex lens, the second one is a biconvex lens, the third one is a positive meniscus, the fourth component is a positive meniscus cemented to a negative one, the fifth one is a meniscus, the sixth one is a positive meniscus, the sevenths one is a biconvex lens, and the eighth component is a biconcave lens. This lens has a large relative aperture (1:0.75).
The limitation of this lens is its small field of view (2Y=180 mm) and an appreciable deterioration of image quality when shifting from the field of view center to its margin (from 0 mm to 180 mm).
A lens is known comprising seven optical components, of which the first two are negative menisci, the third one is a biconcave lens cemented to a biconvex lens, the fourth one is a biconvex lens, the fifth one is a diverging lens cemented to a biconvex one, the sixth component is a biconvex lens with its first surface on the way of optical radiation being aspherical, and the seventh one is a plane-parallel plate. This lens is characterized by a large relative aperture (1:0.8) and a substantial angle of view (2ω=62.3°).
The drawbacks of this lens are its insufficient angle of view and application of the lens with an aspherical surface, which is not adaptable to a streamlined production.
The principles of developing wide-angle lenses are set forth in the paper. The paper presents the methods of selecting the schematic arrangement of the lens that would correspond to the specified parameters. The author describes the photographing lens and the projection lens developed according to the proposed methods. The schematic arrangement of the “Planar” type lens was accepted as a baseline configuration. The drawback of the mentioned lens was its poor light distribution. The basic configuration was supplemented by corrective elements of the wide-angle lenses “Mir” and “Russar”. By means of introducing the power-corrective lens components the main planes of the lens were shifted towards the image plane in order to increase S′F′, and the magnitude of negative distortion was reduced. The photographing lens (FIG. 1) mentioned in the paper was developed using this methods, and it is the closest one to the claimed invention in its essential technical features.
The author has been granted the inventor's certificate for that lens. The lens comprises the aperture diaphragm and seven optical components, of which the first one is a positive meniscus, the second and the third ones are negative menisci with their concave surfaces facing an image side, the fourth one is a positive meniscus, the fifth one is a negative meniscus with its concave surface facing an object side, the sixth component is a positive meniscus having the concave surface facing an object side, which is built up of a biconcave and a biconvex lenses cemented together, the seventh component is biconvex, and the aperture diaphragm is located between the fifth and the sixth components. The lens with its specified characteristics provides high image quality and adequately uniform light distribution. The disadvantages of this lens are its insufficient angle of view (2ω=53°) and small aperture ratio (1:1.4).
The latter invention has been taken as a prototype.